1. Field of the Invention
The present invention relates to a support means for a shoulder belt of a safety belt: system provided with a rolling mechanism in the form of an integrated component of a seat structure of an airplane seat.
2. Description of the Related Art
It is known in the art to subsequently anchor safety belts, particularly the shoulder belts of safety belt systems, to anchoring points intended and specially prepared for this purpose at seat structures of airplane seats, preferably of pilot seats and flight attendant seats. It is necessary for this purpose to provide special reinforcement measures at the seat structures in order to meet the requirements with respect to anchoring to a sufficient extent.
The conditions for permits for the seat structures of airplane seats include dynamic tests in which it is assumed that the seat structures are secured to the floor of a passenger cell and in which it is presupposed that the cell floor is deformed in the case of a crash. Consequently, the seat structures are subjected to significant torsional loads.
In the past, transverse struts in the form of transverse rods or pipes processed in a chip-removing manner were provided in the shoulder areas of the seat structures. These transverse struts were designed to absorb the displacements of the side walls of the seat structures and simultaneously served to deflect the shoulder belts toward the belt anchoring points located approximately on the level of the seats of the seat structures.
However, this known configuration resulted in seat structures having great weights and in very long and heavy seat belts. In the case of the above-described assumed deformation of the floor structure in the case of a crash, the side walls of the airplane seat are displaced relative to each other. Simultaneously, the back rest of an airplane seat is rotated relative to the back of the passenger, represented by a dummy in the approval test, in such a way that only one side of the back rest has contact with the back. A belt constructed in this way is disclosed in DE 36 36 203 A1 which, however, does not have a passage opening in the vertical middle portion which is usually the case in practice for reasons of weight. Because of the resulting longer travel path of one shoulder belt relative to the other shoulder belt in this known belt system, an undesirable loose portion of the belt having the shorter distance occurs. This results in higher belt forces and delays of the dynamic loads, since the initially unsecured shoulder can be held back by the belt only at a later point in time.
However, the forces at the anchoring points of the seat structures to the floors of the passenger cells measured during the dynamic tests are frequently so high that they exceed the strengths of the passenger cell determined by computation. In addition, the delay loads acting on a passenger during an accident must be kept as low as possible in order to prevent injuries to the chest and head. Accordingly, it is attempted in practice to seek to reduce the loads acting at the shoulder belts by using energy converters and force limiting means and, thus, simultaneously to keep the moments occurring at the seat anchoring points as low as possible. If the shoulder belts are deflected as described above, force losses result at the anchoring points of the safety belts of up to 50% relative to those belt forces which are measured between the deflection points and the belt user. If the belt ends are equipped with rolling mechanisms and if energy convertors are additionally to be integrated into the rolling mechanisms, the force levels to be adjusted are so low that the unavoidable manufacturing tolerances may lead to great force differences at the shoulder belts. Consequently, a meaningful reproduceability of the manner of operation of energy convertors/force limiting means for achieving the approval requirements for seat structures of airplane seats is very expensive.
Anchoring systems have the additional disadvantage with respect to costs that, due to the lightweight construction required generally in airplane construction, the housings of the rolling mechanisms are bent out of high-strength aluminum materials. However, such materials require a repeated thermal treatment during the manufacturing process and long processing times.
Finally, another negative aspect of the known constructions is considered to be that tests and maintenance of the belt systems are necessary or required. This is because the belt anchoring systems and rolling mechanisms are integrated into the seat structures because of the narrow space available in such a way that the belt anchoring systems are frequently not accessible without disassembling the entire seat nor are the safety belt systems and the rolling mechanisms capable of disassembly.